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Roland Piquepaille writes "If you're like me, I bet you hate moments when you're in a hurry and all the traffic lights seem to intentionally switch to red just in front of your car. Now, according to Nature, a Belgian traffic researcher thinks that traffic lights that respond to local conditions could ease congestion and reduce your frustration. His method would not give you the individual power to switch the light to green. But if you were part of a group of cars approaching a red light, inexpensive traffic-flow sensors would detect your group in advance and turn the light to green. His simulations show that such adaptive traffic control is 30% more efficient than traditional ways of regulating traffic. However, his system has not been adopted by any large city. So you'll continue to be frustrated by these ?%&$! traffic lights for a while. You'll find more details and references in this overview."

My city has weight sensors laid under the tarmacs, so it knows if there are cars waiting/approaching and switches lights accordingly, or if it shall let the other direction keep going.

The real problem only arises when there are too many cards coming from all directions, and the lights will switch to the "traditional method" that is based on a predefined interval.

It's a catch-22 - Gershenson admits that the benefits wouldn't be as large in a big city where the situation is much more complex than in his simulations, however only bigger city needs to/will consider such traffic control.

Are you sure they are weight sensors? I was under the belief that those sensors worked on the principle of induction. They send a magnetic field up through the pavement, which induces a current in any metal vehicle above. That induced current, in turn, creates a magnetic field which is sent back down through the pavement to the sensor. Works in any temperature and will even dedict lightweight objects like motorcycles.

Try lining up your bike tires with one of the edges of the sensor when you pull up. Once I learned to do this I was able to reliably trip the sensor and get the light to change.

The sensors work off of magnetic induction (like a metal detector) and your bike just doesn't have that much metal to be detected. Positioning yourself along the edge of the road's sensor should trigger the light.

Try lining up your bike tires with one of the edges of the sensor when you pull up. Once I learned to do this I was able to reliably trip the sensor and get the light to change.

In Ottawa, Canada, the majority of lights have sensors, and the vast majority of those sensors are marked with three dots that indicate where bicycles should go to have the best chance of triggering the sensors. The sensors that have those dots are very reliably tripped.

The bike doesn't have to be ferrous. It just has to conduct electicity. Aluminum is actually better than iron for tripping a road sensor.The trouble with bikes is their geometry. The bike's shape offers little capacitance for current flowing perpendicular to the wheels, so only a little bit of induced current flows before an electrostatic field builds up to counter the induced emf.

We actually take citizen complaints of this nature seriously, regardless of if it's someone driving a car or a bicycle. As I nentioned earlier, the only thing is that work load dictates how soon we might be able to address the complaint. We *have* to respond, and document our findings in every instance.

There's one redlight back at my alma mater that doesn't turn unless you trip the sensor; it was either run it, or wait half an hour for a car to show up.

A light along my regular commute had the same problem. I emailed the city's signs & signals department. After a few exchanges, they actually sent some people out to check the adjustment and mark with spraypaint the place where I should place my bike to trip the sensor.

As it turns out, they got it wrong--I eventually figured out I needed to be in a different position.

But the point is that it's worth being persistent--people may be willing to help, and there is probably some reasonable solution.

Around here (In Adelaide Australia), Intersections that have bike lanes, also have a button you can push to signify your presence. Much like the standard pedestrian crossing buttons.
I'd lobby for one of these if I was you. It's far more obvious to the casual biker where it is and how to activate it.

Bicycle riders who want to stay alive stop if both the traffic light and pedestrian light are red.

Some bicycle riders fudge the traffic laws, but the laws are there to keep them safe and should be followed.

I have been commuting to work by bicycle recently and I would never run through a stoplight controlled intersection when both the traffic and pedestrian lights are red. I'll go hit the pedestrian button and wait for the light. Anything else is risking your life.

pull along one edge of the sensor (you should be able to see the saw cut), and lay the bike down on its side across the pickup. Usually you don't have to go all the way down unless the sensitivity adjustment is really far out of whack - just tilting it some should be enough.

What the magnetic sensor is really measuring is flux through a wire loop that it's driving current around. This flux is proportional to the current it's using (which you don't control) and the surface area of the loop. As the signal is

I was picturing a weaker car - something that would likely have more than one wing on the back, and lots of stickers, etc - that requires people to lift up around the drive wheels + set the parking brake in order to do a real burnout. Right now, I'm envisioning the '82 Diesel VW Rabbit a friend had. That thing was rated at something like 50HP, and was only able to smoke the tires in a pubble of tranny fluid with 4 guys lifting up on the front end while the e-brake was set.

Well, they have the capability to detect motorcycles and bicycles, but often the street dept. lowers the sensitivity to the point that only vehicles larger than a small car are detected. This is well documented on many motorcycle discussion boards.

Often times a motorcyclist must wait until a car appears behind them to activate the sensor. Alternate action requires dismounting the bike and pressing the pedestrian button. In frustration some have waited several minutes in the hope a vehicle would appear to trip the light and when none have they finally felt safe to procede only to be stopped and written a ticket. It seems the only way to change the situation is to take it up with the street/highway dept. and/or the local government--not helpful hundreds of miles (km) from home.

Fortunately, there is only one sensor activated light in this town, but one of these days I'm going to be on a day ride and get stuck in one.

A trick I learned a long time ago is to shutoff and restart the motorcycle. The starter motor has enough electrical force to trigger most sensors.

My current bike won't engage the solenoid if the bike is already running. I don't have to shutoff the bike first. I just press the start button real quick and the light turns green. Since most lights are switching to camera sensors this isn't as useful now. Flash the lights a couple of times and the camera will pick it up as motion.

There are devices out there that mount to the bottom of the bike to activate the sensors that work through inductance. I've heard of riders putting a large magnet under the frame. Running the starter is an interesting idea. With the engine cases being aluminum there is not as much magnetic shielding.

I wonder if the starter on my 650 is large enough to do the trick. Alas, she's put away for the winter (well not so put away that I could get it going in a few minutes:).

Well, they have the capability to detect motorcycles and bicycles, but often the street dept. lowers the sensitivity to the point that only vehicles larger than a small car are detected. This is well documented on many motorcycle discussion boards.

Often times a motorcyclist must wait until a car appears behind them to activate the sensor.

Even if the bike was made of plastic and bubblegum you can always trigger the detector if you kill your ignition and then re-start the bike. The windings in the starter motor create a significant electromagnetic disturbance when cranking the engine.

Works in any temperature and will even dedict lightweight objects like motorcycles.

you obviously have not ridden a motorcycle to any stoplights in Chapel Hill (or most of NC, for that matter). Today's generation of sportbikes (with emphasis on lighter weight & materials such as Al) have a hell of a time tripping these things.. if ever. Had someone once suggest a magnetic field induced by kicking the starter motor would trip the signal.. but it only works on rare occasion.

An iPod is most likely to be capacitative, not inductive. I know for a fact that Synaptics touchpads (in most new laptops) are capacitive [synaptics.com]. I believe their web site gives some better tech descriptions.

In order for induction to work, you would have to have a large quantity of metal in your finger.

Are they weight sensors? I never knew. I thought they are electromagnetic or smthg. Anyway, they are everywhere in the US nowadays.

I saw something more interesting a while back in Los Alamos. They had sensors (right near the nuclear lab) that detected you way in advance, and would change the light to green before you got to the intersection (no need to slow down). But they seemed to work only on weekends, when traffic was low.

In parts of San Diego, the traffic lights get completely fucked up at night time, in an attempt to reduce street racing.

Not sure if it's purely timing, or distance sensoring, but either way, it seems to work - that is, piss the shit out of someone like me driving *only* 5-10 MPH over speed limit. After 10PM, the lights turn red on approach no matter what speed you are going.

Where did all the street racers in San Diego go? I remember in 1999 and 2000 every friday and saturday night ~2000 cars would drive around Miramar and Mira Mesa. For the last 2 years I haven't seen them around. I did move to pb 2 years ago, so maybe that is why I have not seen them. Are they still around or have they finally been stopped? I have been to racelegal a few times, but there doesn't seem to be half of the people that used to come out.

The thing about timed streetlights is that they're calibrated for a given speed. If they're, say, calibrated for 30mph and they're 1/4 of a mile apart, they'll turn green every 30 seconds regardless of your speed. If you go "only" 5-10 MPH faster... you just catch a red light, and still don't get home any faster than someone who obeys the speed limit.

I.e., you'd think people would get the idea already that there is really no reward for endangering everyone around. Someone who stuck to the speed limit got home in exactly the same time, and obviously with less stress. Didn't need to use up extra gas accelerating and decelerating all the time either.

And yes, I do mean endangering. Due to the elementary physics fact that kinetic energy is proportional to the square of the speed, so is the braking distance. E.g., the speed difference between 50 km/h and 70 km/h is 40%, but the braking distance _doubles_.

Add poor visibility at night (you might not see a kid dashing to cross the street until he's in front of your beams), the driver _and_ everyone around being tired, etc, and I really _don't_ need people doing "only" 10mph over the limit at night.

And again, as you've noticed, it doesn't even get you home faster. It just makes you stop at the next red light.

But naah... for some people speeding is like _the_ proof of their manhood. Obeying the traffic laws or not driving like an irresponsible maniac, that's like admitting sexual impotence. Or worse.

Erm... more likely the sensors you speak of are based on electric fields not weight. Driving the vehicle over the coil embedded in the road causes a change the inductance. (your car is a big chunk of steel).

There are somes limitations with this type of sensor. Its only has two states, there is a car here, there isn't a car here. No indication as to how many cars are backed up at each light. Also, once you're already stopped at the light, the damage has been done. This system it seems intends to anticip

Some colleagues of mine from Europe were in the states working for a few months. It wasn't prudent for them to purchase a car since they were here for such a short period of time. Since they also lived in the city, public transportation was fine, and walking got them to most places they needed. One night, after some late night partying got them hungry, they wanted to get something to eat. The only place that was open was the late night Wendy's, but it was just a drive-thru. One friend went up to the speaker/automated ordering booth, and stood there waiting...and waiting...before realizing as he stepped aside for a car to go through, that the sensor below allowed the attendant inside to know that there was a car waiting for ordering. He did what any person, half-drunk, hungry from partying would do...he stepped on the sensor and jumped with all his might -- to no avail. Eventually, he sobered up enough to actually walked by the window to talk to a real human. Ahhh...if it wasn't weight sensors, then the mere presence of a human standing on the pad should have activated it, no?

I walked through the Taco Bell with my roommate a few years back - in a Central IL city that houses a major university with a top-ranked Engineering school and borders a city named similarly to an alcoholic beverage - and had the same experience. They took our order, but said that their insurance prohibited them from serving a pedestrian. Like we couldn't have opened the car door, stepped out, smashed the window with a crowbar, and shot the moron just as easily on foot or in a car. Well, opening the car

I delivered pizza's in college. There were no sensors on the streets at the time, but most every intersection had those push buttons for pedestrians.

I made a telescoping probe(two broomsticks wrapped with coat hangers that i could extend to ~10') that I could use on most of the city streets as things were often very tight. Sometimes I would jump out of the car and go press the button. Other times I would yell at pedestrians to please punch the button. And never forget the pizza driver motto: 'No Cop No

When I was in Sweden years ago they had the motion sensors all over everywhere. It wasn't this guy's system of requiring groups of cars, but specifically your car and only kicked in at night. None of this crap in the US where you have to sit on the weight sensors, you just drive normally and by the time you get to the light it has turned green for you! Keep going the speed limit and you'll never overtake a red.

Marvelous system. I couldn't help but think we're behind the times when I experienced the bliss

Ann Arbor, MI has something like this in place. Late at night when there is no cross-traffic on the sensors, if you approach a red light and maintain constant speed at the speed limit (or below), it will turn green in time for your arrival at the intersection!

My old roommate was from there and told me about it, and I had a hard time believing him, but I went up there with him, and got to see them firsthand - they do work, but only at late night when there's no cross-traffic.

They exist and they suck. I have done minor coding on traffic modelling projects for around 4 years back in the early 90-es and I can tell you that they are the wrong idea.

The problem is that if every traffic light reacts only to input from sensors they traffic tends to get into a positive feedback state. This results in the total throughput on a road decreasing instead of increasing. I have been through this calculations several hundred times and no matter what method you use the result is still the same. It sucks rotten eggs compared to having all lights on a road set to fixed sync and having a floating speed limit to accommodate for congestion.

When I was in San Jose, CA a couple of years back, they had a system up where sensors in the road would pick up cars at intersections. They then used microwave antennae to broadcast the information to lights further down the road. So if you were driving along at night with nobody else on the road, you would get long strings of green lights going your way.

"a Belgian traffic researcher thinks that traffic lights that respond to local conditions could ease congestion and reduce your frustration. His method would not give you the individual power to switch the light to green. But if you were part of a group of cars approaching a red light, inexpensive traffic-flow sensors would detect your group in advance and turn the light to green. However, his system has not been adopted by any large city."

I am a traffic engineer, and traffic lights similar to what this Belgian traffic researcher describes already exist. They are called "actuated signals." They work as follows: Loops (not weight sensors, but magnetic loops) are placed in the roadway approx. 300 meters before the traffic light, then 200m, 100m, 50m and 10m. When the light is green for this path, every time a car drives over a loop(assume 300m loop), the green light time is extended long enough for the car to reach the next loop (200m), and so on and so forth until it reaches the 10m loop, where the green light is extended long enough for the car to travel safely through the intersection. Now, if the 300m loop is not reactivated every 3 seconds, the light "times-out" and will turn red once all vehicles have passed through the intersection safely (so if a vehicle is on the 100m loop, the light doesn't just turn red). Additionally, the light has a maximum green cycle time (sum of green and yellow light time), typically 58 seconds. So, if there is a never-ending stream of cars, the light doesn't remain green forever. I hope this clears things up a bit. Also, actuated signals are intended for minor arterials (major collector streets), not for principal arterials (expressways and large intersections).

"His method would not give you the individual power to switch the light to green."

Actuated signals do give you the individual power to switch the light to green.

His simulations show that such adaptive traffic control is 30% more efficient than traditional ways of regulating traffic. However, his system has not been adopted by any large city

I'll guess that the reason why is because a simulation shows this, not a real test. Traffic simulation has been a topic of much research, but as far as I'm aware, little convincing results have emerged... Simulations based on liquid flow do not work (they do not give anything like an average traffic), and those based on drivers modelization (ie, x % of 'aggressive drivers', y % of 'sloppy drivers', z % of 'careful drivers' etc) become incresingly complex and demanding with the scale of the simulation... I'm not aware of anything practical ever done with these (feel free to correct me).

In any case, if his adaptive system does work, it's a breakthrough. I've worked a few years back with people in charge of traffic and roads around Paris, and from what I've been told, nothing like this has ever worked better than static programming (with the exception of multiple programmings for different time of the day). From what I remember, even getting such programming right demands extremely experienced people. Of course, this might be specific to Europe where intersections are rarely perpendicular and often involve "creative" solutions.

You seem to be under the impression that city engineers (and their political bosses) would implement this if they thought it worked. That assumes they want to reduce traffic congestion. I see no reason to believe that is their goal.

You seem to be under the impression that city engineers (and their political bosses) would implement this if they thought it worked

Yes, from experience I can tell you that these people do not like traffic congestions and go to great length to reduce them, regardless of what any individual driver may think when he's sitting in his car and goes through a "red wave" (a set of consecutive road lights designed specifically to reduce speed [that may just be a french term tho]). Slower traffic here may mean smoother traffic there.

Of course that only applies to the people I've worked with, so granted, I'm generalizing.

As an academic who uses simulations alongside formal modeling, statistical analysis, and experiments I can say that most academics know that simulation is a lousy way to "prove" a theory. Think of simulations as extended logic problems: the outcome is completely determined by the assumptions one makes and the inputs one provides to the simulation. No respected academic would suggest that simulations can "prove" the merits of a particular theory.

Simulation is, however, great for one thing: identifying the predictions generated by one's theory given a set of inputs. If you're trying to show that rule A doesn't necessarily predict outcome B, then simulation is useful. If you'd like to prove rule A does predict outcome B (i.e. almost any useful causal statement), then you need to follow up your simulation with empirical analysis.

Simulation says "If I'm right about everything, this is what the world should look like." It doesn't prove that you're right, but it does tell you what evidence you need to examine. Ultimately, if your theory can't predict the real world, it's of little import to most academics.

Traffic lights in the UK have had rubber-strip switch sensors embedded in the roadway before intersections since the 1950s. They have disappeared from sight but I believe they were replaced by a magnetically-sensitive buried strips at some stage in the 70s or 80s.

people won't try to speed ahead anymore instead, they'll stick with a pack

It sounds simplistic but this is the way people drive in New York City, by design. We don't have adaptive traffic lights (that I know of), but they wouldn't really do any good here because during the day the traffic flows at a pretty constant rate in all directions, and at night the lights are programmed to the speed limits on the major thoroughfares.

Believe me, a lot of study has been done into traffic management in major cities like New York, and tweaks to the system occur on a constant basis. But the "pack" is actually the desired effect in a city like this, where one pack of cars travels at the speed limit for a set interval before hitting a red light. Another pack follows them, and the pattern repeats itself on both crosswise and parallel streets. It's really the only way to both keep traffic moving and maintain speed limits. It also cuts down on red light running because you're not going to gain anything by running a red - you'll just end up at the back of the pack at the red light ahead of you. It similarly cuts down on unnecessary lane changes (which only slows traffic flow) because jockeying for position is not important.

Of course, there are still quite a few bad drivers here, but the fact is traffic does flow and adaptive traffic lights wouldn't accomplish anything.

Bah - sensor traffic lights are about the worse thing when looked at from the point of view of the driver (I don't know how good they might be from an overall traffic flow perspective, I'm just using this topic as a jumping board for my rant).

I live in the poxy town of Swindon [swindonweb.com] in England - home of the wierdest traffic management systems in the world, one of which is the Magic Roundabout [swindonweb.com] (which I actually like, but timid drivers wet themselves at the thought of crossing it). On the north side of town, where

Spinning your tires (or wheels, I suppose) will get you off the line slower. When I'm driving like a maniac to get in front, I'm always careful to keep my rear tires just on the verge of slipping during a launch.

Hooray for instant gratification, boo for pointing out that I'm only arriving at my destination 30 seconds faster as a result of all that stress-inducing behaviour.:)

I'm from a city in New Zealand (Hamilton) where we have a self monitoring system tied back to the City Council. Unfortunately it seems to be a little too smart, holding patterns that don't reflect the traffic. As a result, traffic changes its flow each day (drivers choose new routes) which further changes the trending and thus cancels the advantages you'd hope to gain. When the system is out or loops are cut (roadworks) the system reverts to timers/loops which seem to work better. Perhaps it's just when we add users the perfect system suddenly becomes imperfect...

There is at least one set of lights in my city that are timed rather than radar/rollover sensor triggered. The reason is that they are on the main road out of the city to the capital, where ideally there should be no lights/junctions. So the lights are deliberately timed to only allow traffic from the side junctions for a few seconds every few minutes.

But for all out madness, one cannot beat signal-controlled roundabouts. I don't know is anywhere else but Ireland insane enough to use these, possibly the UK, but it's rather run having to randomly stop at red lights while going round a roundabout.

The two main such roundabouts in Ireland are the Red Cow Roundabout in Dublin (the "Mad Cow Roundabout") and the Kinsale Road Roundabout in Cork (the "Magic Roundabout"). Best avoided - but usually unavoidable. Oh yes, I nearly forgot, the former now has a tram system travelling across it too. Fun fun fun.

I thought a majority of traffic lights were already predictive, I thought it was common sense to have this built into the technology when it was first created. If not as mentioned here but at least timed anyway to reflect busy and quiet periods in any given day.
On a side note, It annoys me as a pedestrian when you press the walk button, the green man comes on only when there is no traffic. Not of course when there is traffic and you need to cross the road in safety, thereby stopping the traffic.

Victoria is a very pedestrian friendly city and the ability move around using ones own two feet is cherished and rightly so. It is truly sad that cars trump pedestrains in your culuture.

Sorry, but a lot of Americans have to go to someplace daily for work/school that is just simply too far away to travel to as a pedestrian. Maybe in some of the giant cities you'd have a point, but it doesn't apply to everyone.

Personally, I live ~20 miles from my place of work, so i'm forced to use a car everyday instead of walking. However, I still have many options for getting some exercise - I can ( for example ) do light exercising in my living room, I can go to my apartment complex's fitness center, I can go to the YMCA, or simply jog on the nature trail across the street.

Many people don't (or can't) take the time to do something like that, but that doesn't make the car use the automatic cause of their poor shape.

Pherhaps this is why so many americans are fat asses?

Perhaps instead of being a smartass, you could explain the mystery of how many Americans that don't live within walking distance of everything still manage to stay in shape somehow. Boggles the mind, doesn't it?

Walking along city streets is not the only form of exercise, and "not being able to walk everywhere" is not the reason for people's poor health. Perhaps being forced to walk everywhere would help the matter, but it's certainly not a primary cause - as I said above, it simply removes one avenue for exercise from a list of many.

On the main road in front of Wright State University, there is a series of traffic lights that are perfectly out of phase. I don't if its to annoy students who drive to fast or what, but I feel like a bit in a shift register whenever I drive through there.

I also understand that traffic routing is a complex undertaking, so I do understand any trepidation that traffic engineers or city hall would have in setting this up. It also costs money too, though I bet a lot less than widening the road would.

I hope something like this does work as well as advertised and that it gets deployed. Simulations are one thing, I'd like to see a real world application.

This is really, really old news!!There have been adaptive traffic lights for years (decades?). Most of them nowadays use cameras but some of the early ones using coils embedded in the road are still around.
(And no I'm not referring to the coils that are right at the light to detect waiting vehicles. You'll find the ones for adaptive systems between intersections at the midpoint of the block...).

So WTF, anyway? Is this guy related to Rip Van Winkle? He's got a hell of a lot more tech than that to di

It looks like this system favors large volumes of traffic that flow through a city - the city dweller that is actually living in the city would get blocked by the lave volume of traffic that isn't stopping, and is instead just passing though on a direct route.

So the end result, is that the person who pays for the traffic-signals via taxes gets shafted - and a bunch of out-of-towners begin to use the city as a shortcut.

Great for people who live in the suburbs, but bad for the actual city dweller.

If I should miffed, it's because our small city has wonderfull routes for the yuppies to get to the local Wal-Mart - but those same yuppies won't stop in the core of our city to buy things from the mom-and-pop business that are paying for the nice routes.

There is a major road by my house where all the stoplights are completely screwed up. It almost seems intentional during the day, but at night, you know the lights were designed to turn red when cars approach.

First of all, there are sensors under the cars that are standing right before the intersection. These types of sensors are installed just about everywhere there are stoplights. But if you pay attention, you'll notice that on this street, there are also sensors about 200 to 300 feet back from the intersection. There is a sensor under each lane. By the way, this is a major city street, with three lanes of traffic for each direction.

When driving during the day, there is a lot of traffic, and so you might wonder why in the heck it seems that the cross streets have much longer "green" times than you do.

When driving at night, you'll easily see why. There are usually only a few cars on this street at night. You drive, and you can see that all the stoplights ahead of you as far as the eye can see are GREEN. You drive, and immediately as you pass over the sensor that is 200 to 300 feet back from the stoplight, the light in front of you changes to yellow, and then to red. This happens at a rate that makes it impossible to remain at a constant speed and go through the intersection before it turns red. You'll either have to floor it (and even then it is doubtful whether you'll make it--the yellows are very short), or stop, which is what you'll end up doing.

Now that you're standing at this red light, and the cross street has a green, you'll wonder why you have a red and the cross street has a green, WHEN THERE ARE NO CARS DRIVING ON THE CROSS STREET! Now here is the interesting part. The light could be red for a minute or two, or you might stand there for a long time. As a matter of fact, I noticed that at all of the stoplights on this major street, they will remain red until a vehicle approaches on the cross street. As soon as a vehicle approaches there, his light will change to red and yours will change to green. At 3:00 am, it might take a long time before a vehicle approaches on the cross street. One time, I actually waited ten whole minutes before such a vehicle approached, and only then did his light change to red and mine changed to green.

Now I have been living here for four years, and I have driven down this street enough times at night to tell you that this isn't a casual observation and that I'm not just jumping to conclusions. Others who have driven down this road at night have mentioned the same thing, and I noticed that it never, ever fails. The sensors are all wired such that you will have to wait at EVERY intersection, until a vehicle on the cross street approaches, at which time he will have to wait, and then you get a green light. It's almost as if city workers wanted to play a practical joke and taunt drivers with green lights that remain green for any amount of distance, but only until you actually get near the stoplight. During the day, you don't notice it so much because there is so much traffic that everybody is stuck anyway.

Why the governments couldn't apply some of that facial-recognition technology they're so eager for to actually do something useful, like recogznie traffic, is beyond me. Wait, no it isn't. Never mind.

I have a better idea. They could put cameras in intersections, like the ones that take a picture when you run a red light and you get a ticket in the mail. Ok, they put these cameras, except that not only do they take pictures of actual red light violators, they also take pictures of cars going through the intersection at random times when the light is green and it is perfectly legal to enter. Then, the image is sent to computers, where it is processed to remove other vehicle traffic, to change the lights from green to red, etc.

Then, you drive to work, minding your own business, and you don't run any red lights. In fact, you are the best driver in the world. You don't break a single law. And then you get a ticket in the mail with photographic evidence that YOU ran a red light, even though it never happened. The court will have some internal rule that all such tickets are considered an automatic conviction, and there is no way to appeal. That will enhance revenue.

I have an additional idea. In France they started blanking out the passenger side of the cars in these pictures, because too many Frenchmen got caught with another woman in the cars by their wives opening the traffic ticket that came in the mail. So the automatic image manipulation software that performs the above incrimination would go a step further and put a prostitute in the passenger seat. If you're driving in the evening, say, home from work, special studs in the road can come up and puncture your tires right after the picture of your car is taken. Then, conveniently, there will be a towtruck nearby who offers to take you to the nearest tire shop. The tow truck company and the tire shop will be in some secret business agreement with the city. The studs in the street will be embedded in such a way, and they will puncture the tires and retreat back into the street so fast, so as to be undetected. The tow truck driver will take his sweet time hauling the car to the tire shop, and once there, they will take their sweet time putting new tires on the car. In the meantime, some woman walks into the waiting room where you're waiting, and she comes up and without your permission grabs your head and kisses you right on the face, a wet, nasty kiss. Her tongue practically goes down your throat and out of your ear, like when Madonna kissed Britney Spears. In the meantime, cameras film all of this. Then this woman just gets up and goes away. By the time they finish putting tires on the car, it will be quite late at night. You return home and your wife wonders why you're so late. You tell her that you had a flat tire. The receipt from the tire place has the date and time, and little do you notice, because who checks, that the time is five o'clock, not, like, 10:00 when they actually finish and charge you. Your wife thinks it's kind of funny that it took so long to change a tire. (Also, they hid dirty panties under the passenger seat in your car.) Next thing you know, a traffic ticket comes in the mail during the day when you're at work. Your wife opens it and sees a prostitute in the car with you on the day you came home late. She says what the hell is this, and you explain that there's no way this could be, because this never happened. Your wife is skeptical and starts crying. The next day, a package arrives in the mail. It is a video tape. There is a note that says, "I didn't want to be the one to tell you this but you have a right to know." Your wife puts it in the VCR and it's the video of you macking with some hot woman (the video from the tire shop). Now she's really pissed off. She wants a divorce. Little did you know that the divorce lawyers also had secret business negotiations with the city.

Now that is what I call revenue enhancement in the truest government style. Not only does the government take away your money, but it deliberately fucks up your life as well.

I'll invent a jurisdiction where in certain strategic intersections, at night, all the lights in the intersections will be red, and there will be a no-right-turn-on-red restriction during those times. Cops will be placed all over the place, but they'll be hidden. Then, they'll catch you.

This is generally how your traffic lights work; underneath the tarmac is a series of coils designed to detect cars. If anything his technique is to expand the sensors past the few yards they currently detect, a fairly obvious idea but generally not worth the gain over the status quo and intelligent consideration. Generally speaking traffic at night is just daytime traffic but lighter. You pretty much don't see roving gangs of traffic encountering a series of red lights.

This isn't like normal weight-sensing or magnetic traffic lights. This system is designed to break the traffic down into chunks in such a way that no two chunks will approach the same light at the same time. This way, it can accomodate large amounts of traffic.

If you want to visualize how this might work, watch the episode of Futurama where they go to the planet of human-hating robots, where Fry and Leela are trampled by the robots going to and fro. The "chunks" of

Now I just need one that will recognize my motorcycle at 2am when no cars are around to tigger the lights for me.

I ride a supersport Yamaha YZF-R6. Weighs about 410 wet and I have problems triggering many stop lights, so much so that I have areas I don't ride when traffic is light because they never turn green for me.

Try this [greenlightstuff.com] - a magnet designed to induce voltage across the coils as you move across them. Depending on how the sensor is designed, this voltage may trigger it (otherwise, it would be using the inductance change from the frame of a car)

I ride a supersport Yamaha YZF-R6. Weighs about 410 wet and I have problems triggering many stop lights, so much so that I have areas I don't ride when traffic is light because they never turn green for me.

As noted further up in the comments, there are generally ways you can position yourself so that you'll trip the signal, even with just a bicycle. There are usually visible cuts in the pavement where the sensor lives which you can use to figure out the right position. Google around and you should be ab

US is currently preparing for a completely different thing - a more or less massive roll-out of red-light cameras (the thing where you get you car's photograph in the mail and a red-light ticket). As a preparation for this measure, stop lights are adjusted (most of the time the duration of yellow is simply reduced) in order to increase you chances of running red light, thus increasing the profit generated by red-light tickets. (This will also increase the fatality rate, of course, but this doesn't seem to be a reason for concern.) I'm amazed how much more often these days in California I see cars crossing intersection right under my nose even when I have green. A couple of years ago I'd see something like this about once in a month. These days I see it virtually every day.
In this evironment it is highly unlikely (read - impossible) that US authorities will implement anything tha will to decrease your chances of running red light. Today they prefer to make money by decresing public safety, not by increasing it. So you can forget about anything like "driver friendly" stop light for a while.

The fact that more people are running lights couldn't possibly be the fault of the drivers could it?

Any camera system i've encountered will not flash unless your car is crossing the stop line when the light is red. If you are going the speed limit you should have no trouble making that stop safely. If you are in the intersection or on top of it when the light turns yellow you have nothing to worry about

I thought that it would be a great idea to put an entire city's traffic lights on a private LAN system which monitored for traffic sitting waiting to go through the intersection. (Using whatever method to detect this which is cheapest.)

So instead of having all of those individual boxes out there that cost money to take care of on an individual basis - you just have a simple control box which sends and receives information. Think of it - each light detects if it is working or not and automatically calls for a human to come out and fix it. Lights become more coordinated than before because entire series of lights can all be set to green at one time. Emergency vehicles can carry wireless boxes with an encrypted password on it that tells the lights they are coming up to that they need to get through. And for those who misuse such things, the system could be rigged to monitor where each vehicle is located and if a vehicle is in two places at the same time the fake vehicle could be flagged and stopped by police officers.

How is the signal transmitted? Does the city have to lay hundreds of miles of new cable/DSL/Fiber Optic lines? NO WAY! All they have to do is to do the IP over the electrical lines and suddenly the entire set of traffic lights in any city is connected. You would have to install the proper boxes to listen for and accept the commands from the central server. But it is a lot less in cost than having to lay new communication lines. This might even be possible with wireless communications soon.

So you say: "What about large cities with several small cities within it or nearby? Won't they affect each other?" The answer is: NO - They won't. Remember that with TCP/IP v6.0 you have billions and billions of IP addresses to choose from. I think we can dole out a few thousand from this group for this purpose. Also, the power to the lights are (I believe) on a dedicated circuit which would effectively make all of the lights reside on a private LAN line not available to the public. (So someone would actually have to try to sabotage the lights rather than there being an accidental sabotage by a private individual on the same electrical line.) Filters can keep the two separate (ie: Public and Private IP over the electrical grid.).

Would it be bogged down? Not really. You don't have to be connected all of the time to the light. Only for the few milliseconds it takes to connect, tell the light to change orientation, and then disconnect. Let's say there are 100,000 traffic lights in your city. What do you do? You break it down into lots of 5,000 (so 20 servers). The average web server can handle 5,000 people per second while dealing out static web pages. This should be a snap because the information is a lot less than the average web page. The twenty servers are attached also to a single system which monitors all of the twenty servers by simply flipping between them like a TV monitor camera does. Or you could hire twenty people (one per server) to watch what was going on.

Similar to how monorail systems are monitored presently (only we throw out the static LED display and just use a monitor to display the light's status'), this system only has to keep track of if a light is working or out and can be programmed for different algorithms depending upon what part of the day it is. So rush hour traffic coming into the city is given preferential treatment over cross town traffic. At the evening rush hour the flow is reversed. Otherwise, lights respond according to the sensors. Keeping lights green for on coming traffic and red for empty streets.

Think of it - no more traffic lights that stay red for five minutes or more for no reason. Traffic lights that help you reach your destination. Block crooks from escaping areas by always turning their lights red and blocking their escape by always having the cross traffic moving through the intersection.

Yeah, I know, it's incomplete and ugly but I just wanted to show a general picture. Yeah, this would work for small traffic situations, but, honestly, this could cause a lot of problems (bugs, etc.). Perhaps very limited "learning" traffic lights would be good, but totally self-adapting could cause lots of problems.

- dshaw

Note About the Code: Yeah, i did that in the little Slashdot comment box. It's ugly, unindented, and probably has nonsensical if/then cycles. Please let it be, since it's hypothetical anyway.

Just leave a few minutes earlier... People want to buy these 10 ton SUVs and watch DVDs and play video games in them, listen to satellite radio, drink their Starbucks and eat McDonalds. If you create a vehicle that is nearly as comfortable as your living room, why are you in such a hurry to get out of it? I drive a small Honda Civic, and people will gladly risk my life to whip across 3 lanes of traffic and make a U-turn into WalMart. Trust me, my time IS as valuable as yours, and I am not in that much of a hurry.

In my city, the streets are in a 1-mile grid. The streets every 1 mile are major streets, and there are 1/2 mile streets that are collector roads. I'm not sure I'd want these at major intersections, but where a major street meets a collector road, it would work well. Set it up so that a large group of cars coming on the major road would turn the light green regardless, and then when there arent cars coming, the light would be able to cycle to the collector road and let everyone out.

Assume (for this post) that these devices actually work and improve the efficiency of city streets. This is why you can't find them on your block:

(1) Safety. A lot of effort is spent proving that a traffic control device is safe. When traffic lights screw up and allow opposing green lights, people die. It is entirely unacceptable for a traffic control device to screw up.
So when a city is faced with buying a proven design or a new advanced design that improves efficiency but may be a liability concern, the city will go with the proven design.
I concede that the new system would be tested endlessly, but I claim that any complex system will have flaws that don't show up until deployed in the field. I've seen unbreakable unix systems crash. It happens.
I think that provable safety in this application can (and will someday) be done. I just wouldn't want to be the first city adopting it.
So another option to ensure safety is redundancy such as that used in some airplanes. That is, multiple independant systems working on the traffic problem, and if any of them fail the others will notice. Doing this right costs money, which brings us to point 2.

(2) Cost. My city really doesn't even bother fixing road problems. I went to Berkeley CA the other day and they had enormous potholes that were "fixed" by painting bright colors around them so they could be avoided. If Berkeley doesn't want to spend a couple bucks to patch a hole, then why would your little town bother to consider removing existing systems that cost hundreds of thousands of dollars and replace them with ones that probably cost more?
Further, why would you want your city to spend this money for a marginal improvement in flow? The answer is because some intersections are so terrible that you always are caught up in traffic. These intersections are the bottlenecks that hold up everybody, ones where 30% improved efficiency would be a blessing, which brings us to the 3rd point.

(3) This doesn't help the worst intersections. This switching system would be nice for those pesky lights in your neighborhood that always seem to be red when you arrive, and that you are always first in line and usually the only one to go through in your direction.
I claim that the intersections which could use a 30% improvement the most are those that would not be helped by this system. That is because no matter which side is getting green, every precious second of green light is being used by traffic. This is 100% efficiency, as measured by throughput / theoretical maximum throughput. You can not improve this system by watching for groups of cars, since there are always groups of cars coming.
This would be a neat feature on some intersections, but these intersections aren't the ones that DOT really focuses on improving. The effort involved in making small intersections intelligently switch lights isn't generally worth the cost of doing so.

That said, I'd like to see this in use in my neighborhood, and I'm glad that people are looking into solving traffic congestion problems.

Oh man, this has been bugging me for about ten years. It seems that we already have a system with a built-in method of measuring traffic load via the sensors and a way to control that traffic via red-amber-green lights.

What we currently do with this system is impose on it an artificial set of rules that makes the lights change in a way that is smarter than just alternating every X seconds. But no matter how sophisticated we get, the whole approach is flawed in the same way that a spam filter with a fixed, unchanging set of rules grows less and less effective over time.

The article talks about partially "adaptive" traffic lights, but why not go all the way? I say unleash a bunch of totally Darinistic code modules on traffic lights. Have them mutate, and each generation the ones that score well (by reducing the traffic load they can measure) survive while the rest die off.

Clearly in the beginning the code modules would suck, but then you get a traffic system that is genuinely inhumanly efficient, and adapts to changing conditions. Why can't we have that?

This is what I think about every time I sit at an intersection with nobody coming in the other direction. Am I crazy?

And God I hate them. The cities that have properly timed lights and don't use these stupid sensors, have lower problems with speeding and "Orange Light" runners. Why? because if the lights are timed out to traffic flow staying at one constant speed guarantees you to always be green. In those areas that have the "smart" lights it's a constant traffic jam. Small side roads with a single car every minute, Short lights because backed up traffic is always over the jam detector (a loop device about 100 feet back from the light to signal backup.) Since in both directions there is always traffic over the top of them you get really short lights both ways and a blue ton of people pushing the light, drag racing to the next one to try and get 2 in a row etc. Then you add into the mix the "Left turn traffic" detectors.... ugh. Sometimes low tech is really higher quality and more intelligent.

No thanks. The problem here is that people drive on roads not on simulations. The benifit from these is not signifigant enough to justify the expense. In fact local studies I've seen done in California show that in most cases these lights actually increase polution not decrease it over the long haul.

During high traffic times, they pretty much have to do the normal timed cycle to allow all traffic through.

But, many traffic lights don't need to be fully operational during non-peak times when traffic is low. Where I used to live, in Michigan, they had basic traffic lights, which they would switch to blinking mode in the evenings (the main road blinks yellow, to allow traffic through; the crossroad blinks read, and people proceed through when they can - after stopping).

In California, with an abundance of tax dollars, they use sensor based traffic lights. So, in the evening when I approach the intersection, it detects me, pauses for several seconds, then stops oncoming traffic to allow me through. I have to stop and wait, and oncoming traffic has to stop and wait. So, it's less efficient for all involved.

The net effect is that I seem to get stopped at EVERY traffic light I hit. Their expensive, over-engineered sensor lights don't seem to operate any better at peak times either.

Heck with his system. I just want the computers that they use to monitor the sensors at the light to respond to you if you are there before the light changes. As it is, these systems currently seem to decide what will happen over 5 and sometimes as much as ten seconds in advance of their next step through a cycle. If you get to the red light for a left turn in that time window, the system will completely ignore you and make you sit there (often several minutes) while it goes through a complete traffic cycle and then finally acknowledges you and lets you make that left turn. There is simply no reason with the modern electronics in traffic control devices that this decision could not be made just a fraction of a second before the next step in the cycle. Such a system would be somewhat safer too, as it would be less frustrating to drivers and so would cause less people to cut through the intersections when the lights are against them.

Around 2500 of the intersections in Sydney are linked together and they "marry" and "divorce" each other based on live statistical data as cars flow through the intersections.

It's a self-calibrating system. It has been exported to many countries.

The local intersection controllers measure traffic flows and adjust timings locally and also are linked to regional controllers that share statistics for an area and these regional controllers are all linked to the central monitoring facility in the city.

A friend of mine back in the day used to be a dealer for traffic light systems for Orange and Seminole Counties, FL (Orlando).

There is a device on most intersections in the area that detect EMT and fire vehicles and turn all of the lights on that side of the intersection green as to clear traffic. These sensors hang in between the stop lights.

Another friend of mine claimed that he could flash his hi-beams at night and cause the sensors to think he was an ES vehicle. After speaking with the dealer I found out this guy was full of crap.

Apparently the system works like this:Each vehicle has a strobe on top of the roof. When the siren/lights are activated, the strobe turns on automatically. The strobe flashes in a specific pattern and "activates" the sensor as it approaches the intersection. Behind the strobe however is an IR emmiter which sends a coded signal to the light which apparently identifies the vehicle and then gets logged in the system.

This allows them to track the time and number of the vehicle that went through the stop light turning everything green. It also lets them search for unauthorized uses in the system.

A somewhat unrelated point:Seminole co is the second richest county in the state (other than Palm Beach). They have too much money. These peckerheads like to install traffic lights at intersections even if they are not needed...why? "to slow the traffic down" It pisses me off more than anything. The Central Florida area already has enough traffic problems and these waterheads are trying to slow things down... I guess they won't be happy until we are turned into the industrialized Star Wars planet of "Coruscant" and no one can move anywhere on the ground. http://www.starwars.com/databank/location/coruscan t/index.html

It's no secret that our current government wants to force motorists off the road, either through excessive use of tax, or any other congestion 'saving' scheme that involves more money on our part. For this reason, I don't believe these devices will be used to turn our lights green on approach, but rather to red instead. It's a sad state of affairs, and unfortunately there's nothing that can be done about it.

Seeing as the UK's public transport infrastructure depends extensively on buses since the rail networks are largely overcrowded, there would be no incentive to make them switch to red as it would make public transport worse. You apparently have missed that the major reason the government wants to "force motorists off the road" is because in congested areas it's the easiest way to make public transport faster and less prone to delays.

In London, for example, 70-80% of commuters use public transport, yet the

This technology is sooo new and at ahead of our future that my middle-age village (900 years old now) in south of France had some like this for as far as I remember driving around there (about 15 years). It was actually frustrating to see that those lights would not react to my moped (too tiny...), but the b...d around the corner with his big fat BMW would have the green light kick in ALL the time!.

in our country (philippines), our government purchased lots of "smart" traffic light systems and installed them on major intersections in manila. the problem is that the traffic lights i believe has a hard time adapting to our traffic situation.

what our current traffic management head did is to disable the traffic lights and close intersections on a streth of road. instead u turn slots were placed around every kilometer. traffic eased up because cars do not stop on intersections anymore. there is a continuous flow of traffic.

a very no-tech way of easing the traffic. i would hope that they actually increase the number of roads where they do that. (but i think the problem is space on the road for the u turn slots.)

Hey look over there, it's Mount Gullible! Seriously, that's an urban legend. In some places emergency vehicles use IR (read: not visible light) strobes to activate sensors on the traffic lights but that is the exception, not the rule. If you could somehow flash your high-beams with millisecond accuracy then you might be able to activate some of the sensors. I don't think most incandescent lights can turn on or off quickly enough to signal properly anyway. Finally, whenever the preemption signal is activated a (visible) light on the traffic light flashes. So you're most likely not activating anything. The light changes on its own, just like it does when you press the button to use the crosswalk at most intersections or when you press the close door button on elevators. 95% of the time, those buttons do nothing. 99.9% of the time (there is probably one random traffic light somewhere that changes because light flashes) flashing your brights will do nothing.

7 corners in bailey's crossroads, va definitely has some type of emergency reponse activated system like the one you mentioned above.

I've sat at lights there for more then 5 minutes on occasions where no traffic in any direction goes and then you hear the sirens and see an ambulance wailing by. There's about 7 or 8 different traffic lights for all the different directions you can go on the intersecting roads so they definitely need a system like that in some places that can force reds so emergency vehicle